A HL3 team could essentially function as an independent studio using the Steam platform, with some funding thrown from Valve. Assuming the ROI is positive what exactly is holding them back?
Yep, and that applies to Valve at two levels because Steam dwarfs the ROI of their games, and their forever-games like Counter Strike dwarf the ROI of any singleplayer game they'd ever be able to make. It's a miracle they even got Alyx out of the door, that was a special case since it was part of their larger VR initiative.
And Alyx was probably a huge failure, ROI wise, because nobody buys VR headsets. I know, not "nobody", but by far and large it has remained a super niche market.
They want it to be good? Throwing it at a third party sounds like a good way to get a meh game and then have to release it since you've already spent X$ on it.
A HL3 team could essentially function as an independent studio using the Steam platform, with some funding thrown from Valve. Assuming the ROI is positive what exactly is holding them back?